Abstract

We describe a genome-wide gain-of-function screen for regulators of NF-κB, and identify Rap1 (Trf2IP), as an essential modulator of NF-κB-mediated pathways. NF-κB is induced by ectopic expression of Rap1, whereas its activity is inhibited by Rap1 depletion. In addition to localizing on telomeres, mammalian Rap1 forms a complex with IKKs (IκB kinases), and is crucial for the ability of IKKs to be recruited to, and phosphorylate, the p65 subunit of NF-κB to make it transcriptionally competent. Rap1-mutant mice display defective NF-κB activation and are resistant to endotoxic shock. Furthermore, levels of Rap1 are positively regulated by NF-κB, and human breast cancers with NF-κB hyperactivity show elevated levels of cytoplasmic Rap1. Similar to inhibiting NF-κB, knockdown of Rap1 sensitizes breast cancer cells to apoptosis. These results identify the first cytoplasmic role of Rap1 and provide a mechanism through which it regulates an important signalling cascade in mammals, independent of its ability to regulate telomere function.

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Acknowledgements

We wish to thank the Agency for Science Technology and Research, Singapore (A*Star) for funding and support to the V.T. laboratory. I.M.V. is an American Cancer Society Professor of Molecular Biology, and holds the Joan and Irwin Jacobs Chair in Exemplary Life Sciences. This work was supported in part by grants from the Leducq Foundation, Meriaux Foundation, Ellison Medical Foundation, Ipsen/Biomeasure, Sanofi Aventis, and the H.N. and Frances C. Berger Foundation. We thank T. Murphy and N. Tonnu for help with the intial investigations involved in this work. We are grateful to B. Li and T. De Lange for Rap1 deletion constructs and P. Lieberman for the Rap1 shRNA vector. We thank J. Karlseder for helpful discussions.

Author information

Author notes

    • Sourav Ghosh
    • , Hendrik Luesch
    • , Arkasubhra Ghosh
    •  & Ee Tsin Wong

    These authors contributed equally to this work.

Affiliations

  1. Laboratory of NFκB Signaling, Proteos, Singapore 138673, Singapore.

    • Hsiangling Teo
    • , Arkasubhra Ghosh
    • , Ee Tsin Wong
    • , Najib Malik
    • , Marc Wong
    •  & Vinay Tergaonkar
  2. Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85440, USA.

    • Sourav Ghosh
    •  & Lisa J. Speiser
  3. Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, USA.

    • Hendrik Luesch
  4. Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA.

    • Hendrik Luesch
    • , Anthony Orth
    • , Paul de Jesus
    • , Enrique Saez
    • , Peter Schultz
    •  & Sumit K. Chanda
  5. Department of Pathology, St. Joseph's Hospital and Medical Center, Phoenix, AZ 85004, USA.

    • Anthony S. Perry
    •  & Jeffrey D. Oliver
  6. CNS Tumour Research Laboratory, Translational Genomics Research Institute, Phoenix, AZ 85004, USA.

    • Nhan L. Tran
  7. Infectious and Inflammatory Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.

    • Sumit K. Chanda
  8. Laboratory of genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.

    • Inder M. Verma

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Contributions

H.T., A.G., E.T.W., N.M., M.W. and V.T. carried out biochemical experiments with Rap1, generated Rap1-mutant mice and helped in data analysis. S.G., A.S.P., J.D.O., N.L.T. and L.J.S. carried out the analysis of Rap1 in human cancers and also helped in data analysis. H.L., P.D.J., A.O., E.S., P.S., S.K.C. and V.T. carried out the genome-wide screen and helped in data analysis and initial characterization of Rap1 as an NF-κB regulator. S.K.C., I.M.V. and V.T. did the project planning and data analysis.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Vinay Tergaonkar.

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DOI

https://doi.org/10.1038/ncb2080

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